Here's why:
* The "i" in "mimic" is followed by a consonant ("m"). This usually indicates a short vowel sound.
* The "i" in "mimic" does not have a long vowel sound marker. Long vowel sounds are often marked with a silent "e" at the end of a word (like "mite"), a double vowel (like "meat"), or a vowel digraph (like "pie").
Therefore, the vowel sound in "mimic" is short, similar to the "i" sound in words like "bit" or "sit".